The present invention is directed to a transfer type heat-sensitive recording device in which an ink donor sheet is used to record data by means of thermal transfer on a recording sheet which is supplied to the recording section independently of the supply of an ink donor sheet.
In thermal or heat-sensitive transfer type recording devices the recording operation of data is generally carried out in the same manner. A recording sheet such as a plain sheet of paper is placed on an ink donor sheet coated with solid ink which is sublimated or liquified by heat in a specific pattern. A heat pulse is applied to the ink donor sheet which is in intimate contact with the recording sheet so that the sublimated or liquified ink is transferred onto the recording sheet.
An example of a conventional heat-sensitive transfer type recording device is shown in FIG. 1 wherein a conveying system is adapted to supply an ink donor sheet and a recording sheet to the recording section independently of each other. An ink donor sheet 1 is supplied from a supply roll (not shown), passed through a recording section A comprised of a thermal head 2 and a backing roll 3, and is moved in the direction of the arrow through a separating section B comprised of the backing roll 3 and a drive roll 4. Finally, the ink donor sheet 1 is taken up on a winding roll (not shown). A separate individual recording sheet 5 is delivered to the recording section A and is moved over the heat generating elements 2A of the thermal head while being held in intimate contact with the ink donor sheet 1 by the cylindrical wall of the backing roll 3. In this operation, the heat generating elements 2A generate heat in a selective pattern to transfer the ink onto the recording sheet 5. Thereafter, the recording sheet 5 passes between the backing roll 3 and a drive roll 4 while still in contact with the ink donor sheet. At this point, the direction of movement of the ink donor sheet 1 is changed abruptly along the cylindrical wall of the drive roll 4. However, since the recording sheet 5 cannot follow this abrupt change in direction of the ink donor sheet, the recording sheet will be separated from the ink donor sheet. The separated recording sheet is advanced in the common tangential direction (as indicated by the arrow) relative to the backing roll 3 and the drive roll 4 and is discharged into a receiving tray (not shown).
In the conventional heat-sensitive transfer type recording device described above, the contact pressure of the drive roll 4 as applied to the backing roll 3 is set at a considerably high value, for instance 8 Kg/cm.sup.2. This high value is necessary for the drive roll 4 to overcome the frictional resistance in the recording section A to thereby move the ink donor sheet 1 in a stable manner in the scanning direction. However, when the engagement pressure of the drive roll 4 is set at a very high value, the contact pressure between the ink donor sheet 1 and the recording sheet 5 is increased temporarily. As a result, during the separation of the recording sheet 5 from the ink donor sheet 1, a certain amount of ink remains on the ink donor sheet which should have been transferred. If this phenomenon occurs, the recording density is decreased on the corresponding portion of the recording sheet. Therefore, the recorded image is considerably reduced in quality.